Bacillus subtilis as a Tool in Basic Science and Applied Research

by Imrich Barák (Institute of Molecular Biology, Slovak Academy of Sciences)

Tuesday 27 Jan 2015, 14:30 → 15:30 Europe/Berlin

AER17/5.14-5.16 (European XFEL GmbH)

Bacillus subtilis is an internationally-recognised model microorganism, whose physiology, biochemistry and genetics has been studied for decades. Our research is oriented toward studying the proteins involved in basic processes in B. subtilis as cell division, sporulation and programmed cell death. The lecture will cover broad range of results explaining the mechanism of the basic cell processes in B. subtilis and its potential in biotechnological exploitation. It will concentrate on basic science questions as i) How the cell knows with high precision to find its center? ii) How the cell knows when to start to sporulate? iii) How the asymmetry in gene expression is programmed? iv) Why the unicellular organism is programmed for self destruction? How the resistant spore coat is assembled and can it be used for novel nano-biotechnology? The main focus of the lecture will be the formation of spore coat structures. When challenged by starvation, Bacillus subtilis produce a dormant cell type, called a spore. Spores are distinctive by a unique capability to withstand extreme environmental conditions. Fundamental importance to spore resistance but also for its germination is the coat. The coat is proteinaceous multilayered shell that provides mechanical integrity and excludes large toxic molecules while allowing small nutrient molecules to access germination receptors beneath the coat. Spore coat is formed by over 70 proteins, ranging in size from about 6 to 70 kDa. The process of the coat assembly which is rather poorly understood, represents a central objective of our research. We are focusing on a group of coat proteins, called morphogenetic which act in controlling the deposition of the various coat components around the forming spore. We examined the protein-protein interactions between these proteins using genetic, biochemical and biophysical methods. Our data imply that due to the physical association the crucial morphogenetic proteins can form a basic skeleton where other coat proteins would be attached. Consequently we investigated the self-assembly properties of spore coat proteins by electron microscopy. Currently, there are no structural information about the individual coat components. In order to gain insights into the structure of the spore coat of B. subtilis we have prepared a set of recombinant coat proteins and analyzed these proteins both as single species and in combination. A number of self-assembled structures including two-dimensional crystals and helical fibers were discovered thus clearly indicating that coat proteins have an intrinsic tendency for self-organization into higher order assemblies.